Apparatus and method of disc clamping for disc stack assembly

ABSTRACT

An apparatus and method for balancing a disc stack assembly of a disc drive where a clamp is used as a counter-balance as well as for securing a disc to the disc stack assembly. The clamp and spindle motor are configured for positive engagement and alignment with the use of a minimal number of parts. The clamp includes a cavity through which a protrusion or a shaft of the spindle motor hub may extend. The clamp may be further secured in a desired orientation by the use of a single fastener.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. Provisional Application No. 60/341,322 filed on Dec. 13, 2001.

FIELD OF THE INVENTION

[0002] The present invention relates generally to disc drives. More particularly, the present invention relates to an improved disc clamp and motor hub assembly for use in a disc stack assembly (DSA) for a disc drive.

BACKGROUND OF THE INVENTION

[0003] Modern computer systems store data in devices or components internally or externally for later usage. There are various types of storage devices for which the computer systems could read/write data from/to the devices One of the most widely used devices for storing massive amount of data in a computer system is a disc drive having a DSA.

[0004] The capacity of a disc drive depends on the numbers of tracks on the surface of the disc. When more tracks are formatted on a disc, the precision at which the transducer could read from or written to disc becomes critical. There are a number of reasons that could cause the reading/writing process to be inaccurate, for example, imbalance of the disc drive, etc. Imbalance of a disc drive may be caused by the uneven distribution of mass about the axis of rotation of the DSA. Such imbalance may be the result of the disc shifting in a radial direction, sometimes known as “disc slip”, which in turn may cause inaccurate positioning of the transducer. When the number of tracks on the disc greatly increase, any imprecise positioning of the transducer becomes more critical to the overall performance of the disc drive.

[0005] There are a number of ways to reduce the imbalance of the DSA in a disc drive. For example, by biasing the disc(s) and spacer(s) in opposite directions with reference to the center of the motor shaft, and thereby having substantially equal mass distributed around the motor shaft longitudinal axis. While various devices and methods may be known for balancing a DSA, it is a continuous challenge to reduce the number of components and to simplify the steps in assembly so as to achieve greater manufacturing efficiency.

[0006] The present invention provides a solution to reduce the instability of the disc drive and at the same time reduces the use of spacers and/or balancing rings so as to Cut down the production cost, and also provides other advantages over the prior art.

SUMMARY OF THE INVENTION

[0007] The present invention relates to disc stack assembly (DSA) which includes, by way of example and not limitation, a clamp and a motor hub that could provide a solution to the above-mentioned problem.

[0008] In one embodiment of the invention, a DSA includes a motor shaft defining a vertical axis and a motor hub surrounding the motor shaft, the motor hub being rotatable about an axis of rotation. A disc is mounted on the motor hub where a clamp is used to tighten the disc on the motor hub by a fastener. The shaft protrudes from the motor hub for engagement with a hole of the clamp. The clamp may be formed and biased such that in assembly with the DSA, its center of mass does not coincide with the axis of rotation, so as to provide a counterbalance to the DSA. The direct engagement of the clamp to the shaft, or an equivalent extension from the motor hub reduces the number of components required to align and retain the clamp in a desired orientation for balancing the DSA. Using the same engagement, the clamp can be secured to the DSA, thereby fulfilling another of its function, that of securing the disc to the motor hub.

[0009] The motor hub includes a sunk-in portion in the middle of an upper surface of the motor hub. A clamp is to assemble with the motor hub so that it clamps the disc to the motor hub. Within the DSA the motor shaft extends through the motor hub but does not protrude beyond an upper surface of the clamp when the clamp is in a post-depressed position. The clamp is installed on the hub by aligning an opening in the clamp with the motor shaft protrusion. A tight tolerance is established between the opening of the clamp and the outer surface of the motor shaft so as to prevent the disc from moving out of alignment. The clamp is then tightened onto the motor hub with a fastener. An engagement feature located along the inner diameter of the clamp ensures a positive engagement between the clamp and the fastener.

[0010] According to another embodiment of the present invention, the clamp has a greater height reference than the motor shaft protrusion. This will enable the motor shaft not to protrude beyond the upper surface of the clamp at the post-depressed position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a diagrammatic plan view of a disc drive constructed in accordance with an embodiment of the present invention.

[0012]FIG. 2 is a cross-sectional view taken generally along line 2-2 of FIG. 1 where a single disc is clamped on the motor hub.

[0013]FIG. 3 is an isometric view of a clamp of one embodiment of the present invention.

[0014]FIG. 4 is a cross sectional view of a motor hub of one embodiment of the present invention.

[0015]FIG. 5 is an enlarged detail of a portion of the disc drive assembly of FIG. 2 illustrating one embodiment of the present invention.

[0016]FIG. 6 is an enlarged detail of a portion of the disc drive assembly of FIG. 2 of an alternative embodiment of a clamp.

[0017]FIG. 7 is an enlarged detail of a portion of the disc drive assembly of FIG. 2 of an alternative embodiment of a motor hub.

[0018]FIG. 8 is an enlarged detail of portion of the disc drive assembly of FIG. 2 of an alternative embodiment of a motor hub and clamp.

DETAILED DESCRIPTION

[0019]FIG. 1 illustrates a plan view of a disc drive 100 having a base 102 and a cover 104 in assembly with the base 102. After the various components have been installed on the base 102, the disc drive 100 will be firmly sealed by the cover 104 to maintain a clean internal environment. A circuit board (not shown) attached to the bottom of base 102 controls most drive operations, such as the operation of the spindle motor and read/write operations. Connector 124 leads to a flexible printed circuit cable 122 which in turn is operably connected to other circuitry for receiving and transmitting data and/or commands between the circuit board and actuator arm assembly 112. Details of the circuitry operations are not presented herein as they are well known to a skilled artisan.

[0020] Data is read from or written to concentric tracks on a disc 110 by a transducer 120. A DSA 106 includes a spindle motor 212 that rotates the disc 110. During drive operations, the disc 110 is rotated at a high speed while the transducer 120 is held over a desired track of the disc 110. The transducer 120 is coupled to an actuator arm 114 via a suspension 118 which is rotatable about a pivot assembly 115. A voice coil motor 130, attached to the other end of the actuator arm, controls the rotation and positioning of the actuator arm.

[0021]FIG. 2 shows a partial cross sectional view of a DSA 206. A motor shaft 210 defines an axis 230 of rotation substantially perpendicular to the base 102. A motor hub 204 is coupled with the motor shaft 210 via one or more bearings 222. The motor hub 204 provides a planer surface 218 which an annular disc 220 could essentially be rested. The disc 220 includes an inner edge 224 and an outer edge 226 where the inner edge 224 is abutted with a cylindrical surface 216. In assembly, the disc 220 is clamped tightly on the motor hub 204 via a clamp 208. A fastener 215 which engages the motor shaft 210 is used to tighten the clamp 208 to the motor hub 204. During drive operations, the disc 220 mounted on the motor hub 204 is rotated about the axis 230 at a constant speed. A spindle motor 212 mounted on the base 102 enables the rotational movement.

[0022]FIG. 3 illustrates an isometric view of a clamp 301 according to one embodiment of the present invention. The clamp 301 is stamped to have a cylindrical sunk-in portion 303 surrounding a center opening 302 and a contact portion 304 at the circumference of the clamp 301. A protrusion 310 encircling the center opening 302 is provided with a thickness greater than an inner boundary 311 of the clamp 301. This provides positive contact with the fastener 215 when the fastener 215 threadably engages the motor shaft 210. A tight tolerance may be established between the outer surface 211 of the motor shaft 210 and the inner boundary 311 of the clamp 301. At least one notch 316 is defined by the center opening 302. The contact portion 304 includes a circular furrow 314 adjacent with a distal end 318. After the disc 220 is clamped on the motor hub 204, the circular furrow 314 provides a line contact between the clamp 301 and disc 220. Somewhere along the distal end 318 of the clamp 301 is defined with an indention feature 320 to act as a balancing feature.

[0023] In a modern automated assembling process, one or more machinery arms are used for aligning components together to form a whole. Therefore, a design of the clamp 301 is defined with plurality of apertures 315 on a convex surface 307 for handling by locating members (not shown). A preliminary alignment may be performed by aligning the apertures 315 with alignment features 415 of the motor hub 401.

[0024] According to one embodiment of the present invention, a motor hub 401 as shown in FIG. 4 is coupled on a motor shaft 410 via one or more bearings 422. The motor hub 401 has a center opening 412 for which the motor shaft 404 could extend further through the motor hub 401 to form a protrusion 405. The motor hub 401 further includes an inner rim portion 414 and a disc support portion 420. An annular disc 220 is essentially rested on the planar surface 418 of the disc support portion 420, with at least part of the inner edge 224 of the disc 220 in abutment with at least part of a cylindrical surface 416. Then the clamp 301 is loaded on top of the motor hub 401 to clamp down the disc 220. Subsequently, the cylindrical sunk-in portion 303 of the clamp 301 will horizontally rest on the inner rim portion 414. During the assembling process, the alignment feature 415 is known for use to incorporate with the aperture 315 for the preliminary alignment. Subsequently, the motor shaft protrusion 405 is inserted to the center opening 302 of the clamp 301, for which, the inner edge 211 of the clamp 208 abutting with an outer surface 408 of the motor shaft protrusion 405, for a fine alignment with the motor hub 401 before it is tightened with the fastener 215.

[0025] FIGS. 5 to 8 shows the enlarged details of a portion of FIG. 2 of the present invention having a motor hub 204, a motor shaft 210, a fastener 215 and a clamp 208. A portion 501/601/701/801 illustrates the stage where the clamp 208 and the fastener 215 are at a pre-depressed position while a portion 502/602/702/802 illustrates the stage where the clamp 208 and the fastener 215 are at a post-depressed position.

[0026] Prior to a fine alignment of the clamp 208 relative to the motor hub 204, one embodiment of the present invention as illustrated in FIG. 5 shows that a motor shaft 508 provides an alignment feature 516 extending from a center opening 505 of a motor hub 504. A clamp 510 has an inner boundary 532. The inner boundary 532 provides a positive engagement 522 with an outer surface 534 of the motor shaft 508.

[0027]FIG. 7 shows another embodiment of the present invention with a motor hub 704 providing an alignment feature. A ring 716 attached on a surface 736 of the motor hub 704 providing a protrusion feature. A clamp 710 has an inner boundary 732 that provides a positive engagement 722 with surface 734 of the motor hub 704. Such aspect may require a fastener 706 to be connected to the motor hub 704 directly.

[0028] Optionally, one other embodiment of the present invention as illustrated in the FIG. 8, is such that a motor hub 804 may be assembled with a clamp 810 with some fine alignment between the motor hub 804 and the clamp 810. The clamp 810 has an alignment feature 842 protruding from a bottom surface 834 of the clamp 804. A groove 840 located surrounding the center of the motor hub 804 is configured to provide an interference fit with the alignment feature 842.

[0029]FIG. 5 also illustrates the clamp 510 having a protrusion 518 surrounding the center opening 505 of the clamp 510 prior to clamping. The protrusion 518 is required to have a positive contact 528 between a clamp surface 538 and a fastener 506. This could be performed by ensuring the height dimension 526 of the inner boundary 532 of the clamp 510 is greater than the height dimension 524 of the alignment feature 516 while the clamp 510 is fastened as shown on the portion 502.

[0030] One embodiment of the present invention as illustrated in FIG. 6 has a clamp 610 fastened on a motor hub 604. A clamp 610 includes a support portion 612 wherein at least a height reference 626 of a support portion 612 is greater than a height dimension 624 of an alignment feature 616. Therefore the height difference provides a positive contact 622 between a clamp surface 628 and a fastener 606 while it is post-depressed on the motor hub 604.

[0031] As mentioned in FIG. 7, the motor hub 704 provides the alignment feature whilst maintaining a positive engagement 728 between a surface 738 and the fastener 706. This is achieved by ensuring a height dimension 726 of the inner boundary 732 of the clamp 710 is greater than a height dimension 724 of the ring 716 while the clamp 710 is fastened as shown on the portion 702.

[0032] Another embodiment of the present invention is illustrated in FIG. 8. The clamp 810 has an alignment feature 842 protruding from a bottom surface 834 of the clamp 810. As the alignment feature 842 essentially provides a positive engagement 812 between the clamp 810 and a fastener 806 while preserving a fine alignment for the clamp 810 on the motor hub 804.

[0033] Alternatively described, one embodiment of the present invention provides for an assembly (such as 206) including a spindle motor (such as 202) that has a hub (such as 204) configured for rotation about an axis (such as 230) and an extension (such as 405) protruding from the hub (such as 204) along the axis (such as 230) by a protrusion length. The assembly also includes a clamp (such as 301) that has an inner edge defining a hole (such as 302) for receiving the extension (for example, 405).

[0034] The inner edge (such as 518) of the clamp (such as 301) may have a thickness or reference height that is no less than the protrusion length. The extension (such as 405) may be a rotable shaft (such as 410) of the spindle motor (such as 202) or it may be formed as a unitary body with the hub (such as 204). Optionally, the inner edge of the clamp (such as 301) is configured for interference fit with an outer surface of the extension (such as 405). In one embodiment, the clamp (such as 301) further includes an indentation feature (such as 320) such that its center of mass does not coincide with its geometric center. The indentation feature (such as 320) may be formed at an outer edge (such as 318) of the clamp. The assembly (such as 206) may further include a fastener (such as 215) which in engagement with the extension (such as 405) comes into abutment with the inner edge of the clamp (such as 208). In engagement with the fastener (such as 215), the clamp (such as 208) may be resiliently deformed. In one embodiment, the assembly (such as 206) may also include a disc (such as 220) that is held against the hub (such as 204) of the spindle motor by a contact portion (such as 314) of the clamp. According to another embodiment of the present invention, there is provided a disc drive (such as 100) having a disc (such as 220), a spindle motor (such as 212), a clamp (such as 301) and a fastener (such as 215). The hub (such as 204) of the spindle motor (such as 212) is configured for bearing the disc (such as 220) in rotational motion about an axis (such as 230), with the extension (such as 405) protruding from the hub (such as 204) along the axis (such as 230) by a protrusion length. The clamp (such as 301) has an inner edge defining a hole (such as 302) for receiving the extension (such as 405). The fastener (such as 215) in engagement with the extension (such as 405) comes into abutment with the inner edge of the clamp (such as 301).

[0035] Optionally, the disc drive (such as 100) is configured such that the inner edge (such as 518) of the clamp (such as 301) has a thickness or reference height that is no less than the protrusion length. In one embodiment, the disc drive (such as 100) is such that the extension is a rotatable shaft (such as 508) of the spindle motor (such as 212). In an alternative embodiment, the disc drive (such as 100) is such that the extension (such as 405) and the hub (such as 204) are formed as a unitary body. The disc drive (such as 100) may be configured such that the inner edge of the clamp (such as 301) is configured for interference fit with an outer surface of the extension (such as 405). Alternatively, the clamp (such as 301) further includes an indentation feature (such as 320) such that its center of mass does not coincide with its geometric center. A method of biasing the clamp (such as 301) and the disc (such as 220) in opposite directions with reference to the center of the motor shaft (such as may be incorporated the indention feature (such as 320) to provide a counter-balance to the DSA. The indentation feature (such as 320) may be formed at an outer edge (such as 318) of the clamp (such as 301). In engagement with the fastener (such as 215), the clamp (such as 301) may be resiliently deformed. In one embodiment, the disc (such as 220) is held against the hub (such as 204) by a contact portion (such as 314) of the clamp (such as 301).

[0036] It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the present invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the shape of the notches 316 may be found differently from that illustrated in FIG. 3, may vary depending on the particular application for the disc drive while maintaining substantially the same functionality without departing from the scope and spirit of the present invention. In another example, although the foregoing describes embodiments of the present invention in the context of a single platter disc drive, they could also be applied in on multiple-platter disc drives where more than one disc is mounted to the motor hub. In addition, although the embodiments described herein are directed to a disc clamp with a motor hub for a data storage system, it will be appreciated by those skilled in the art that the teaching of the present invention can be applied to other systems, without departing from the scope and spirit of the present invention. 

What is claimed is:
 1. An assembly comprising: a spindle motor comprising: a hub configured for rotation about an axis; and an extension protruding from the hub along the axis by a protrusion length; and a clamp having an inner edge defining a hole for receiving the extension.
 2. The assembly of claim 1 in which the inner edge of the clamp has a height reference that is no less than the protrusion length.
 3. The assembly of claim 1 in which the extension is a rotatable shaft of the spindle motor.
 4. The assembly of claim 1 in which the extension and the hub is formed as a unitary body
 5. The assembly of claim 1 in which the inner edge of the clamp is configured for interference fit with an outer surface of the extension.
 6. The assembly of claim 1 in which the clamp further comprises an indentation feature such that its center of mass does not coincide with the axis.
 7. The assembly of claim 6 in which the indentation feature is formed at an outer edge of the clamp.
 8. The assembly of claim 1 further comprising a fastener which in engagement with the extension comes into abutment with the inner edge of the clamp. 9 The assembly of claim 8 in which the clamp is resiliently deformed by engagement with the fastener.
 10. The assembly of claim 8 further comprising a first disc, the first disc being held against the hub of the spindle motor by a contact portion of the clamp.
 11. A disc drive comprising: a first disc; a spindle motor comprising: a hub configured for bearing the first disc in rotational motion about an axis; and an extension protruding from the hub along the axis by a protrusion length; a clamp having an inner edge defining a cavity for receiving the extension; and a fastener which in engagement with the extension comes into abutment with the inner edge of the clamp.
 12. The disc drive of claim 11 in which the inner edge of the clamp has a height reference that is no less than the protrusion length.
 13. The disc drive of claim 11 in which the extension is a rotatable shaft of the spindle motor.
 14. The disc drive of claim 11 in which the extension and the hub is formed as a unitary body
 15. The disc drive of claim 11 in which the inner edge of the clamp is configured for interference fit with an outer surface of the extension.
 16. The disc drive of claim 11 in which the clamp further comprises an indentation feature such that its center of mass does not coincide with the axis.
 17. The disc drive of claim 16 in which the indentation feature is formed at an outer edge of the clamp.
 18. The disc drive of claim 11 in which the clamp is resiliently deformed by engagement with the fastener.
 19. The disc drive of claim 11 in which the first disc is held against the hub by a contact portion of the clamp.
 20. A disc drive comprising: a base; a disc stack assembly rotatably mounted to the base; and means for balancing the disc stack assembly.
 21. The disc drive of claim 20 in which the disc stack assembly comprises: a spindle motor having a hub with a central extension; and a disc carried on the hub, wherein the means for balancing comprises a clamp for securing the disc to the hub, the clamp being in engagement with the central extension at an inner edge.
 22. The disc drive of claim 21 in which the central extension is a rotatable shaft of the spindle motor. 